its digital - go for the cheapest - there will be no difference - because
it's a string of 1's and 0's - not an analogue sound.
ignore the ripoff merchants.

Thats what I was thinking. Either it will work or no work (nothing
inbetween).

Looks like the 5metre roll for £1.49 will do it then (just about stretch it
rather than use 6m!)

thanks